Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$60.91	11.360%	$67.8294	$67.83	$67.85	$67.80
Purchase #2	$47.31	12.430%	$53.1906	$53.19	$53.20	$53.20
Purchase #3	$24.47	4.238%	$25.507	$25.51	$25.50	$25.50
Purchase #4	$159.63	11.726%	$178.3482	$178.35	$178.35	$178.30
Purchase #5	$154.86	4.353%	$161.6011	$161.60	$161.60	$161.60
Purchase #6	$164.78	4.380%	$171.9974	$172.00	$172.00	$172.00
Purchase #7	$59.40	6.625%	$63.3353	$63.34	$63.35	$63.30
7 purchase totals =	$671.36		$721.8090	$721.82	$721.85	$721.70